Coal is an attractive source of energy because coal reserves are substantially larger than those of oil and natural gas. Traditionally, energy is obtained from the coal by burning the coal directly in a furnace to form high temperature gases. Energy in the form of heat is transferred from the high temperature gases amd may be transformed into work by raising and passing steam through a steam turbine.
In gas turbine engines, hot working medium gases are expanded through a turbine to produce work. One approach to using coal as a source of energy in a gas turbine engine is to first pulverize the coal and to subsequently burn the coal in a combustion chamber of the engine to form the hot working medium gases. Burning coal directly in the engine produces ash and these ash particulates cause damage to the engine as they pass through the engine degrading the service life and the performance of the engine. A second approach to using coal is to first process the coal to obtain combustible gases or liquids. The combustible fluids, either gases or liquids, are cleaned of ash and pollutants and are then burned in the gas turbine engine to produce the hot working medium gases.
Some gasification processes for producing combustible gases also form a carbon rich by-product called char. The char is normally recycled until all of the carbon is gasified. Burning the char directly in the gas turbine engine would improve the gasifier output and cycle efficiency, but, as is the case with pulverized coal, burning the char produces abrasive particulates which may damage the turbine. Accordingly, scientists and engineers are seeking ways to utilize the full heating value of coal without exposing the engine components to abrasive particulates.